1. Field of the Invention
The present invention relates to load control devices for control of the power delivered from an alternating-current (AC) power source to an electrical load, and more particularly, to an ambient light threshold adjustment procedure for a load control device that is operable to control the electrical load in response to detected occupancy and ambient light conditions.
2. Description of the Related Art
Typical load control devices are operable to control the amount of power delivered to an electrical load, such as a lighting load or a motor load, from an alternating-current (AC) power source. Wall-mounted load control devices are adapted to be mounted to standard electrical wallboxes. A dimmer switch comprises a controllably conductive device (e.g., a bidirectional semiconductor switch, such as, a triac), which is coupled in series between the power source and the load. The controllably conductive device is controlled to be conductive and non-conductive for portions of a half-cycle of the AC power source to thus control the amount of power delivered to the load (e.g., using a phase-control dimming technique). A “smart” dimmer switch (i.e., a digital dimmer switch) comprises a microprocessor (or similar controller) for controlling the semiconductor switch and a power supply for powering the microprocessor.
An electronic switch (i.e., a digital switch) comprises a controllably conductive device (such as a relay or a bidirectional semiconductor switch), a microprocessor, and a power supply. In contrast to a smart dimmer switch, the controllably conductive device of an electronic switch is not controlled using the phase-controlled dimming technique, but is controlled to be either conductive or non-conductive during each half-cycle of the AC power source to thus toggle the electrical load on and off. Digital dimmers and switches may further comprise occupancy detection circuits such that the dimmers and switches are able to operate as occupancy sensors to automatically turn on lighting loads in response to the presence of an occupant (i.e., an occupancy condition) and automatically turn off the lighting loads in response to detecting the absence of an occupant (i.e., a vacancy condition).
Such a digital device may further comprise an ambient light detector such that the device will only turn on the lighting load in response to an occupancy condition when the detected (or measured) ambient light is below a predetermined ambient light level threshold. This provides energy savings as the lighting load is not turned on unnecessarily (i.e., the lighting load is not turned on in an already brightly illuminated space each time an occupant is detected). However, the value of the predetermined ambient light level threshold may not be suitable in some applications and may require adjustment once the device is installed. Some prior art digital devices do not provide for the predetermined ambient light level threshold to be adjusted once the device is installed. Other prior art digital devices may comprise a dedicated mechanism such as a knob or button for adjusting the value of the ambient light level threshold. However, such a dedicated mechanism adds additional cost to the device. Further, such a mechanism may not be visible to a user once the device is installed in a standard wallbox, thus the user may not realize that such a mechanism exists or that the ambient light level threshold can even be adjusted.
Therefore, there exists a need for an improved method of adjusting the ambient light level threshold of a digital load control device.